Missiles and rockets are commonly stored on and launched from payload platforms positioned on frames. These frames can be stationary in nature, or they can be mounted on motorized vehicles in order to provide greater flexibility in the deployment of the missiles or rockets. In general, such cargo platforms are pivotably mounted on the frame such that the platform and the missiles mounted thereon can be stored and transported in a substantially horizontal position and can be readily elevated to a substantially vertical deployed position by pivoting the platform upwardly about one end of the platform.
Boom structures are frequently utilized to raise or lower a bucket containing an operator or to move an antenna from a stowed position to an elevated operational position. When such boom structures are mounted on a vehicle, it is desirable that the stowed position of the boom avoids significantly increasing the height of the vehicle.
Several actuator systems have been developed in order to facilitate the pivoting of platforms or booms between a substantially horizontal storage position and an elevated or deployed position. Actuator systems of this type typically must address significant mechanical and spatial constraints. For example, these systems must be capable of generating large forces in order to effect the pivoting and lifting of the platform or boom to the deployed position, particularly when the platform or boom is in or near the horizontal storage position. In order to provide the substantial force necessary to initially elevate the platform or boom from its stowed position, it is common for the actuators to be mounted at a large acute angle to the horizontal or even perpendicular to the horizontal, frequently resulting in a portion of the actuator extending above the stowed position of the platform or boom. However, despite this need for significant mechanical strength, it is desirable that actuator systems be constructed such that they impose only minimal interference with the operation of the vehicle or its cargo, e.g., in the mounting, positioning, and launching of missiles mounted on the payload platform. In addition, clearance space between the frame on which the actuator system is mounted and the ground is often limited due to stability and mobility considerations. Thus, actuator systems must be constructed such that they are capable of operation within a limited clearance space between the ground and the stowed position of the platform or boom.
Some actuator systems have attempted to avoid the above-referenced ground clearance limitation by placing all or a significant portion of the actuator system above the upper surface of the platform or boom. Although actuator systems of this type can provide advantageous mechanical characteristics, they ordinarily interfere with the loading and unloading of cargo on the platform surface, often necessitating the use of a crane in order to effect the proper positioning of the cargo on the platform. Similarly, the height of the actuator systems can interfere with the operation of the boom system throughout 360.degree. in a horizontal plane. This need for such specialized equipment can pose a serious limitation to the efficiency and effectiveness of such actuator systems. In addition, the presence of an actuator system extending above the top of the vehicle may pose restrictions with respect to the overhead clearance required for operation of the vehicle.
One conventional actuator, which avoids the projection of the actuator above the platform in the stowed position, utilizes a floating scissor linkage wherein two scissor blade elements are joined about a common pivot, with the distal end of one scissor blade element being pivotably mounted on the frame and the distal end of the other scissor blade element being pivotably mounted to the platform, and with an actuator being connected between the scissor blade elements. However, not only does this require a more complicated mechanical linkage, the distance between the longitudinal axis of the actuator and a line parallel thereto extending through the pivot mounting the platform to the frame at the time of the initial application of a lifting force to the platform by the actuator is relatively small, thereby requiring a very large and powerful actuator to effect the initial upward movement of the platform from the stowed position. Also, the distance between the longitudinal axis of the actuator and a line parallel thereto extending through the point about which the scissor blade elements pivot relative to each other, which determines the effective moment arm, is very small as the platform approaches the full deployed position, thereby requiring only a small movement of the actuator to complete the final portion of the deployment and making the fully deployed platform susceptible to undesirable movements resulting from variable wind forces.